/*
 *    EWMAClassificationPerformanceEvaluator.java
 *    Copyright (C) 2007 University of Waikato, Hamilton, New Zealand
 *    @author Albert Bifet (abifet at cs dot waikato dot ac dot nz)
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package moa.evaluation;

import moa.AbstractMOAObject;
import moa.core.Measurement;
import weka.core.Utils;

public class EWMAClassificationPerformanceEvaluator extends AbstractMOAObject
		implements ClassificationPerformanceEvaluator {

	private static final long serialVersionUID = 1L;

	protected double TotalweightObserved;
	
	protected double alpha;

	protected Estimator weightCorrect;
	
	protected class Estimator {

		protected double alpha;
		protected double estimation;
		
		public Estimator(double a) {
			alpha = a;
			estimation = 0;
		}
		public void add(double value) {
			estimation += alpha * (value - estimation);
		}
		public double estimation() {
			return estimation;
		}
	}
	
	public void setalpha(double a) {
		this.alpha= a;
		reset();
	}
	
	public void reset() {
		weightCorrect = new Estimator(this.alpha);
	}

	public void addClassificationAttempt(int trueClass, double[] classVotes,
			double weight) {
		if (weight > 0.0) {
			this.TotalweightObserved += weight;
			if (Utils.maxIndex(classVotes) == trueClass) {
				this.weightCorrect.add(1);
			} else
			    this.weightCorrect.add(0);
		}
	}

	public Measurement[] getPerformanceMeasurements() {
		return new Measurement[] {
				new Measurement("classified instances",
						this.TotalweightObserved),
				new Measurement("classifications correct (percent)",
						getFractionCorrectlyClassified() * 100.0) };
	}

	public double getTotalWeightObserved() {
		return this.TotalweightObserved;
	}

	public double getFractionCorrectlyClassified() {
		return this.weightCorrect.estimation();
	}

	public double getFractionIncorrectlyClassified() {
		return 1.0 - getFractionCorrectlyClassified();
	}

	public void getDescription(StringBuilder sb, int indent) {
		Measurement.getMeasurementsDescription(getPerformanceMeasurements(),
				sb, indent);
	}

}
